The Equations of motion

Q. Average velocity of a particle moving in a straight line, with constant acceleration $a$ and initial velocity $u$ in first $t$ seconds is:

1. $u$

2. $u+at$

3. $u+\frac{at}{2}$

4. $\frac{u+at}{2}$

Q.

A bus starts from rest and attains a speed of 54 km per hour in 10 seconds. What will be the acceleration of the train?

Q.

The time of ascent is equal to

1. Time of journey

2. Time of descent

3. Both

4. None of these

Q.

A stone is dropped from the roof of a building takes $4\mathrm{s}$ to reach ground. The height of the building is :

1. $19.6\mathrm{m}$

2. $39.2\mathrm{m}$

3. $156.8\mathrm{m}$

4. $78.4\mathrm{m}$